Somewhere along the line, the "structured content+stylesheet=dynamically rendered page" equation broke down. Javascript began to flex its Turing Complete muscles and today we are staring down the barrel of a completely different concept of a web "page"...

According to him, the landscape of applications in the Web 2.0 era is changing; HTML is increasingly becoming a host to “applications”, delivered to the browser via the web.

… because HTML […] allows JavaScript payloads. But if 99% of my pages are 99% JavaScript and 1% declarative markup of content, am I serving out content or serving out programs?

He warns of the danger of a time when content will no longer be as freely available in the web, only to be replaced with “programs” that abstract the access to web-content as we know it. As to why AtomPub may not see much adoption, he believes that

When history is written, I think it will show that without the visual nature of the Web, it never would have taken off as an IT substrate.

He refers to Hugh Winkler's REST hypothesis, in which, Hugh suggests that the fundamental difference between the visual web and the “Atom applications” is that

…. the real, browser plus HTML web has, that RESTful systems don't, is the user agent. The human in front of her browser. An intelligence that reads and understands the meaning of "Author name" and "Title", and fills in an HTML form using queries against her personal database, stored in her brain. [Plus as a side benefit you also] get to present your own user interface.

Paul Fremantle’s post in response to Joe Gregorio’s post, likens the internet to an Anglican Church, and he sums it up saying that the internet is home to a diverse set of applications and protocols, of which AtomPub is just another player ...

[… and] any protocol that gets even a small market share of the Internet is a success. No protocol is ever going to take over the Internet, and there will always be plenty of different approaches to do the same thing. That is simply the nature of the Internet.

Is AtomPub really a failure? The relevant posts are available here, here and here.